337 



nitric acid ; in this experiment there was no subfluoride of 

 iron formed, but the vessel was found to contain fluosiHcic 

 acid gas. 



** In a third experiment a piece of charcoal was employed, 

 which had been previously freed from all metallic impurities 

 and from silica, by being first boiled in pure nitric acid, and 

 afterwards in hydrofluoric acid. Employing this purified 

 charcoal as the positive electrode, I obtained no immediate 

 action upon the litmus paper ; but after the action had conti- 

 nued for two hours, it was found to be completely bleached, 

 while the gold had undergone no sensible action. That the 

 bleaching was not due to the action of the vapour of hydro- 

 fluoric acid was ascertained, by leaving litmus paper for 

 several hours in the neck of a platinum retort, from which 

 hydrofluoric acid was distilling. 



" The battery was now kept in action for fifteen hours, at 

 the end of which time the vessel being examined, the litmus 

 had disappeared, and the gold leaf showed signs of having 

 been strongly acted upon, having assumed a dark brownish 

 colour, and having gathered itself into little balls, as if it 

 had undergone the action of heat. The platinum wire was 

 acted upon in those parts where it was in contact with the 

 charcoal, but no where else. 



" When the platinum wire forming the positive electrode 

 passed through the stopper to the bottom of the vessel, the 

 hydrogen, in place of rising through the perforation in the 

 stopper, as in the former instance, rose now into the re- 

 ceiver, where, upon applying a light, it exploded, showing 

 that it does not enter into combination with fluorine without 

 the aid of heat. The presence of the vapour of hydrofluoric 

 acid in the vessel prevented me from determining by other 

 experiments how far fluorine was a supporter of combustion. 



" To determine the colour of the gas, a stopper of fluorspar 

 similar to the former was made to fit one of the transparent 

 fluorspar receivers formerly described. The gas evolved in 

 the receiver appeared colourless. 



